Input Device and Input Method

1. An input device which switches between input modes according to an external input, said input device comprising: a coordinate input unit configured to identify input positions as the external input using coordinates, the input positions each being detected in response to proximity of an object to or pressure on an input surface defined by a two-dimensional coordinate system; a coordinate-sequence storage unit configured to store, in a coordinate sequence including one or more sets of coordinates which represent coordinate points, one or more of the input positions identified by said coordinate input unit within a predetermined time; and an input-mode determination unit configured to switch said input device to a geometric-figure input mode in the case where the number of the sets of coordinates included in the coordinate sequence is smaller than a predetermined number and the coordinate points are within a predetermined distance range, the geometric-figure input mode being a mode which allows inputting a ready-made geometric figure.

2. The input device according to claim 1 , comprising: a start-point coordinate storage unit configured to calculate, from the one or more sets of coordinates included in the coordinate sequence, coordinates of a start point for drawing the ready-made geometric figure; and a line-to-draw sequence generation unit configured to draw the ready-made geometric figure in the case where said coordinate input unit obtains a new coordinate sequence when said input device is in the geometric-figure input mode which allows inputting a ready-made geometric figure, the ready-made geometric figure being drawn based on the coordinates of the start point and one or more sets of coordinates included in the new coordinate sequence.

3. The input device according to claim 2 , wherein said line-to-draw sequence generation unit is configured to calculate coordinates of an end point and draw a straight line in the case where the number of the sets of coordinates included in the new coordinate sequence is smaller than a predetermined number and coordinate points represented by the sets of coordinates included in the new coordinate sequence are within a predetermined distance range, the straight line being drawn based on the coordinates of the start point and the coordinates of the end point.

4. The input device according to claim 2 , wherein said input-mode determination unit is configured to calculate average coordinates from the one or more sets of coordinates included in the coordinate sequence stored in said coordinate-sequence storage unit, and determine the average coordinates as the coordinates of the start point.

5. The input device according to claim 2 , wherein said input-mode determination unit is configured to calculate medians of the one or more sets of coordinates included in the coordinate sequence stored in said coordinate-sequence storage unit, and determine the calculated medians as the coordinates of the start point.

6. The input device according to claim 2 , wherein said line-to-draw sequence generation unit is configured to calculate representative coordinates and draw a circle having the start point at a center of the circle and a point represented by the representative coordinates on a circumference of the circle in the case where the number of the sets of coordinates included in the new coordinate sequence are equal to or greater than a predetermined number or coordinate points represented by the sets of coordinates included in the new coordinate sequence are out of a predetermined range.

7. The input device according to claim 2 , wherein, when information stored in a current-input-mode information storage unit indicates that said input device is in a geometric-figure input mode, said input-mode determination unit is configured to determine whether or not the new coordinate sequence obtained by said coordinate input unit is in response to an input by tapping, and, in the case where the new coordinate sequence obtained by said coordinate input unit is not in response to an input by tapping, determine to switch said input device to a geometric-figure input mode which allows inputting an ellipsis having the start point represented by the coordinates stored in said start-point coordinate storage unit at a focus of the ellipsis, and calculate, based on the coordinates included in the new coordinate sequence, two sets of coordinates which represent two points to be on a circumference of the ellipsis, and said line-to-draw sequence generation unit is configured to generate a line-to-draw sequence which indicates the ellipsis having the start point represented by the coordinates stored in the start-point coordinate storage unit at the focus and the two points represented by the two sets of coordinates calculated by said input-mode determination unit on the circumference of the ellipsis.

8. The input device according to claim 7 , further comprising an input-mode timer which measures time, wherein said coordinate input unit is configured to reset said input-mode timer when an input of a coordinate sequence is completed, and, when a predetermined time has elapsed since the resetting, said input-mode timer switches the geometric-figure input mode indicated by the information stored in said current-input-mode information storage unit back to an input mode which the information indicated immediately before the geometric-figure input mode which allows inputting a ready-made geometric figure.

9. A method of receiving an external input used in an input device switching between input modes according to the external input, the input device including a coordinate input unit, a coordinate-sequence storage unit, and an input-mode determination unit, said method comprising: identifying, using the coordinate input unit, input positions as the external input using coordinates, the input positions detected in response to proximity of an object to or pressure on an input surface defined by a two-dimensional coordinate system; storing, in a coordinate sequence including one or more sets of coordinates which represent coordinate points, one or more of the input positions identified in said identifying within a predetermined time, the coordinate sequence being stored in the coordinate-sequence storage unit; and switching, using the input-mode determination unit, the input device to a geometric-figure input mode in the case where the number of the sets of coordinates included in the coordinate sequence is smaller than a predetermined number and the coordinate points are within a predetermined distance range, the geometric-figure input mode being a mode which allows inputting a ready-made geometric figure.